1. Field of the Invention
The present invention relates to a recording medium, a producing method thereof and an inkjet recording method that uses the same.
2. Description of the Related Art
An inkjet recording unit has a simple configuration and high quality image recording may be realized through inkjet recording using the inkjet recording unit. Ink used in inkjet recording is controlled such that a viscosity thereof is substantially from several mPa·s to 30 mPa·s such that it may be discharged from an inkjet head, and configured such that the surface tension may be substantially from 20 to 40 mN/m.
In order to control the viscosity of the ink to within this range, an ink solvent is usually contained in the ink at an amount of from 50% to 90% by mass. Examples of ink solvents include water, organic solvents, oils and photopolymerizing monomers. From the viewpoint of the environmental aptitude in particular, water is frequently used. Furthermore, in order to inhibit clogging due to drying of the ink solvent at a discharge nozzle of an inkjet head, a high boiling point solvent such as glycerin is generally used as an ink solvent.
However, when an ink solvent is present in a large amount in a ink drawn recording medium, image blurring and color mixing between colors are likely to be caused due to the abundancy of the ink solvent. Accordingly, inkjet-only paper 200 (see FIG. 5) having a solvent absorption layer (ink-receiving layer) that absorbs the ink solvent and has a thickness of substantially 20 to 30 μm is used as a recording medium, thereby inhibiting image blurring and color mixing.
Furthermore, in the case of aqueous ink where water is used as an ink solvent, water permeates into the base paper at the time of recording to cause paper deformation such as curling. However, as shown in FIG. 5, when a recording medium has a solvent absorbing layer 22 on a base paper 21, water is inhibited from permeating into the base paper; accordingly, the paper may be inhibited from deforming.
In this case in particular, when a graphical image having a high image density or having a high image area ratio is to be formed, an ink amount on a unit area on the recording medium increases, making it difficult for a solvent absorption layer to inhibit the ink solvent from permeating into the base paper. Accordingly, a water resistant paper covered with a resin layer that uses polyolefin (such as laminated paper) is generally used.
Inkjet technology has been applied recently not only in the fields of office printers and home printers but also in commercial printing. In the field of the commercial printing, rather than paper that has a photograph-like surface that completely shuts out the ink solvent from permeating into a base paper, paper having printing texture similar to general printing paper is demanded. However, when a solvent absorbing layer that forms part of a recording medium becomes as thick as 20 to 30 μm, the surface glossiness, texture and hardness of the recording medium are limited; accordingly, inkjet technology in the commercial printing field is applied only to posters and ledger sheets printing in which the surface glossiness, texture and hardness of a recording medium may be limited.
Furthermore, owing to the adoption of the solvent absorbing layer and water resistant layer, the recording medium becomes expensive, and this is also a limiting factor.
As a technology related to the above, in order to improve color development characteristics and to inhibit bleeding and ink strike-through from occurring, a recording sheet formed by disposing an ink-retaining layer made of at least a filler, a water-soluble polymer and an aqueous emulsion resin on an anti-ink permeation layer containing an aqueous emulsion resin has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 3-234698). In order to improve the wet tensile strength, and a dissociation property and an ink setting property upon recycling, a coated paper obtained by sequentially disposing a water resistant layer including an SBR resin having a predetermined glass transition temperature, and a printing layer including a filler-coated layer has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2002-69890). Further, a printing coated paper in which, in order to improve blister resistance and glossiness, two or more coated layers are disposed on a surface, and an undercoat layer adjacent to the uppermost layer includes a predetermined thermoplastic adhesive, has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 10-168791). An image receiving paper provided with a paper support having thereon a water-repelling layer containing a binder and a filler, and an ink receiving layer in order to improve the water resistance has been disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 11-78224).